Signage employed with roadway systems has been the subject of regulatory and institutional investigation essentially since the emergence of the motor vehicle. The structural characteristics of road or highway signs vary from major bridging entities to the relatively small and ubiquitous stop sign. Regulations and specifications promulgated for signage extend not only to a standardization of their visual cuing aspects, but also to vehicular safety considerations. For example, the Federal Highway Administration evaluates sign structures for conformance with the AASHTO (American Association of State Highway Transportation Officials) "Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals", as well as the NCHRP (National Cooperative Highway Research Program) Report 350 entitled "Recommended Procedures for Safety Performance Evaluation of Highway Features".
The mounting or supporting structures for stop signs and the like, generally are categorized as "small sign supports". Traditionally, the designs for these small supports have been based upon two considerations. First, their mounting should be sufficiently robust to withstand torsional and other stresses associated with wind loads. When typically mounted upon single sign posts, stop signs and the like become airfoils to wind loads with resultant induced torsional and other stresses. A traffic control sign such as a stop sign can pose serious hazards when blown down by virtue of its cuing absence. Secondly, it is reasonably anticipated that such signs will be struck in the course of roadway accidents. Accordingly, they must be designed to break away under specified impact conditions such that they present no danger to vehicle occupants. For example, as an errant vehicle strikes a signpost, the post should break away such that no part of it penetrates the passenger compartment and no passengers experience a negative change in relative velocity greater than 5 meters per second. To assure appropriate breakaway characteristics, many signposts are provided having two components. A first lower support or anchoring component is provided which is driven or otherwise secured in the ground with a small portion of it, for example about 4 inches, protruding from terrain surface. Then, an elongate upper component carrying the sign at one end is attached to the protruding portion of the lower component using a splice form of connection and connectors or fasteners having a breakaway characteristic such as break away bolts which fail under predetermined tensile stresses. Fortuitously, certain of the signposts also are observed to break additionally at the point of impact with a vehicle.
Signpost structures may take on a variety of cross-sectional configurations and generally are formed of steels which may exhibit a variety of characteristics. The cross-sectional configurations may, for example, be round or pipe-like, or very often are formed as flanged channels having a cross-sectional shape somewhat emulating a hat. Steel forming such posts generally exhibits a brittleness, and the completed post structures particularly are subject to failure in wind load induced torsion. In order to provide a splicing interconnection between the two signpost components adequate to overcome wind loads, it is necessary that the two post configurations abut or nest together and that they be fastened by break away bolts which are spaced an adequate distance apart, typically four inches. Generally, the posts will be formed having spaced apart apertures along their central lengths which field personnel align and then install breakaway bolts at specified vertical spacings. A difficulty earlier has been identified in connection with the splicing together of nested channel-formed signpost components. In this regard, the component cross-sectional configurations often do not nest. When this occurs, the breakaway bolts may be subjected to excessive moment induced stresses to cause premature failure of the signs under wind load. Granger addressed this problem in an approach described in U.S. Pat. No. 5,125,194 entitled "Safety Signpost with Break Away Connection", issued Jun. 30, 1992. With the early Granger approach, field personnel were called upon to install spacers between the channel sections such that the contact surfaces of the channel sections were brought together against the spacer notwithstanding their failure to otherwise nest. To provide such correction procedures, field personnel are trained and provided with written and diagrammatic instructions as to the use of the spacers and requisite splice spacing of the break away bolts.
In practice, however, it has been observed that such procedures often are not followed, due in part to the physical difficulties encountered by field personnel while erecting signs under even mild wind conditions. Frustrated under such circumstances, such field personnel will ignore requisite longitudinal bolt spacing and omit spacers. The result may be the subsequent loss of signage due to wind load induced torsional stress.